“Children born dependent on heroin and other opiates may be more likely to perform poorly academically as they get older, according to a new study from Australian researchers.

The study examined more than 2,200 children born with neonatal abstinence syndrome and compared their test results with those of more than 4,300 who do not have NAS, as well as the test results of 598,000 children in New South Wales.

The biggest takeaway, the authors concluded, was that children born with neonatal abstinence syndrome, or NAS, performed progressively worse on testing as they got older. By seventh grade, nearly 38% of the NAS children did not meet the minimum standards in at least one testing category.